How to deform a "plane"
I would start with a flat plane in “Top View”. Cut it in half and add a “Mirror Modifier”. Select the edge where you want the bend to take place then press “Shift” + “S” and select “Cursor to Selected” from the drop down menu.


Then change the “Pivot Center” to the 3D Cursor.



Then select the part of the plane you want to rotate and rotate around the 3D Cursor constrained to the “Y” axis. Press “R” + “Y” to accomplish this.



Then add a “Solidify Modifier”